Radio frequency apparatus



Feb. 28, 1961 R. H. MARLOWE RADIO FREQUENCY APPARATUS Filed Jan. 25;1960 FlG.l.

INVENTOR: RICHARD H. MARLOWE,

United States Patent "ice RADIO FREQUENCY APPARATUS Richard H. Marlowe,Clinton, N.Y., assignor to General Electric Company, a corporation ofNew York Filed Ian. 25, 1960, Ser. No. 4,341

4 Claims. (Cl. 31539) My invention relates to radio frequency apparatusand pertains more particularly to improved voltage tunable magnetroncircuitry including a rcentrant resonator cavity.

The reentrant resonator cavity has heretofore been utilized extensivelywith klystron amplifiers and oscillators. Its use with voltage tunablemagnetrons has, however, been limited because of diflicult-iesencountered in endeavoring to obtain broadband operation of thev mag-.

netrons with such a circuit. My invention contemplates the provision ofa compact, efiicient voltage tunable magnetron circuit including areentrant cavity and effective for serving as 'a variable frequencysource operable in equipments requiring tunabili-ty over a substantiallywide operating frequency range.

Accordingly, the primaryobject of my invention is to provide a new-andimproved voltage tunable magnetron circuit including a reentrantresonator cavity. 7

Another object of my invention is to provide anew and. improved voltagetunable magnetron circuit which is etficient and adapted for operationover a substantially wide operating frequency range. Another object ofmy invention is to provide a new and improved voltage tunable magnetroncircuit which is compact and relatively simple and inexpensive tomanufacture.

Further objects and advantages of my invention will become apparent asthe following description proceeds and the features of 'novelty whichcharacterize my in vention will be pointed out with particularity in theclaims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide a circuitincluding an interdigital voltage tunable magnetron having apair ofspaced anode contact rings and a reentrant resonator cavity. The cavityhas the opposed end walls thereof apertured for receiving opposed endsof the magnetron and for serving as coaxial electrical contacts adaptedfor making circumferential contact with the anode rings. Extendinglaterally from one side of the circuit is a. coaxial line. .The outerconductor of the coaxial line is secured to the cavity and the innerconductor includes a substantially J-shaped flattened inductive loopextending inwardly in the cavity and having the end portion thereofdisposed between the anode rings with the turned back portionelectrically contacting one of the anode rings. Insulative means in thecavity hold the inductive loop in desired inductive relation with themagnetron.

For a better understanding of my invention reference may be had to theaccompanying drawing in which:

Figure 1 is a greatly enlarged sectionalized side elevational view ofradio frequency apparatus incorporating an embodiment of my invention;and

Figure 2 is fragmentary plan view illustrating particular features of myinvention.

Referring to Figure 1, there is illustrated therein a voltage tunablemagnetron generally designated 1. The

- magnetron 1 can be of the type disclosed and claimed in copending US.application S.N. 723,926 of G. I. Grifiin,

2,973,455 Patented Feb.- 28, 1961 2 I r. et al. entitled Voltage TunableMagnetron, filed March 25, 1958, now Patent No. 2,930,933, and assignedto the' same assignee as the present invention. Briefly, the mag netron1 is constructed to include stacked alternate ceramic and metalelements. The ceramic elements generally include a plurality ofcylindrical ceramic wall sec tions 2 and an apertured disc-like ceramicend cap 3. The metal members are suitably brazed to or between opposedsurfaces of the ceramic elements to complete a hermetically sealedenvelope and include a metal end cap 4 carrying a cylindricalnon-emissive cathode 5 extending centrally in a cylindrical spacedefined by a plu rality of anode segments generally designated 6. The

anode segments 6 are arranged in a pair of interdigital sets, with eachsegment being carried by a washer-like anode contactring 7. -The rings 7are sealed between a pair of ceramic cylinders -2 and are thus mutuallyinsulated. A filamentary emitter 8 is suitably mounted on the ceramicend cap 3 with leads sealed therethrough and connected to a. pair of.button-like contact members 9 bonded to the outer surface of the ceramicend cap, A frusto-conical control electrode 10 is sealed between one ofthe ceramic insulators 2 and the ceramic end cap 3 and is positionedabout the emitter 8. By means of a lead not shown and which extends alsoin a sealed manner through the ceramic end cap 3 an electricalconnection is made between the control ring 10 and a third button-likecontact member v11 bonded to the outer surface to the ceramic end cap.

T m netron i adapted fornremfinswh ax y aligned with a magnetic fieldprovided, for example, by a magnet including opposed pole piecesdesignated N and S in the drawing. Additionally, the magnetron isadapted for operating with suitable direct current potenv tials on thevarious electrodes supplied through the metal end cap 4 and the contactbuttons 9 and 11 in a manner not shown.

The radio frequency circuit of the apparatus illustrated includes theanode segments 6 and the contact rings 7. Additionally, this circuitincludes as an essential part thereof a reentrant resonator cavitygenerally designated 12. The cavity 12, as seen in Figure 2, can becircular and can comprise a cup-like body having a cylindrical outerside wall 13, a reentrant bottom 14 which includes a cylindrical innerwall 15 and a transverse end wall 16. Additionally, the cavity includesa washer-like cover 17 held in place by a plurality of machine screws.18, for example.

The bottom 16 is centrally apertured for receiving one end of themagnetron 1 and for affording a coaxial contact surface adapted formaking circumferential electrical contact with one of the anode rings 7.The cap 17 receives. the opposite. end of the magnetron and makescircumferential electrical contact with theother anode ring 7 through anannular retaining member 19 threaded in the cap in. amanner to. engagethe other anode ring and hold the magnetron tightly in place in thecavity.

During operation of the magnetron strong magnetic fields are establishedbetween the anode rings 7 in the cavity 12, and provided fortransmitting radio frequency energy out of the cavity 12 is a coaxialline 20. The line 20 includes tubular outer conductor 21 suitablymounted in the side wall 3 of the cavity and extending radiallyoutwardly therefrom. The inner conductor 22 of the line 20 includes anend portion extending radially inwardly and shaped to define asubstantially J-shaped inductive loop adapted for coupling energy fromthe cavity into the coaxial line.

The loop 23 is flattened such as to define a cross section which issubstantially wider than the cross section of the portion of the innerconductor in the tubular portion 21. Additionally, the inductive loop 23extends sutficiently inwardly to dispose the looped end portion betweenthe anode contact rings of the magnetron. Still further, the extremeinner end portion 24 or the portion which turns back on the main portionof the flattened loop rests on and engages electrically the planarsurface of one of the anode rings 7: The portion 24 is preferably ofsubstantiallength and width to insure substantial areal contact betweenthese members. Additionally, the lengthofi the J'- shaped portion andthe substantial width thereof provides for maximum linking orinductiverelation with the magnetic flux present in the cavity during operationof the magnetron. Electrically speaking, this arrangement af fords averytight coupling between the load represented by the coaxiallineand-the magnetron I with-thedcsi'red efiect of lowering the Q of thecircuit; With the Q K thus lowered the circuit is adapted for moreeflicient operationover a substantially wide rangeofoperating'frcquencies of the magnetron.

asses reentrantresonator-cavityhavingsaidmagnetronmounted said anoderings.

therein and including a cylindrical inner side wall, a radially spaced,relatively longer cylindrical outer side wall and longitudinally spacedapertured transverse end walls, said end walls including coaxial contactsurfaces each making circumferential electricaLcontact with one of saidanode rings, a coaxial line including outer and inner conductors, saidouter conductor extending from the outer side wall of said cavity, and said innen conductor in, cluding an inductive loop portiondisposedi'externally 'of said envelope of said magnetron and'extending'in'wardly in said cavity: and between radiallyrprotmding.portions of 2. A combination according 'to'claim 1, wherein saidinductive loop is substantially J-shaped and the turned I back endportion thereof engages and electrically contacts In order to hold theloop 23' in place in the desired position between the anode rings 7, Ihave provided an insulative support member 25. By way of example, themember 25 can be formed satisfactorily of Teflon. Additionally, and asseen in Figure 2, themember 25 is slightly wider than the flattenedportion of the loop 23, thus to prevent rotation of the loop and'therebyinsure support of the loop in the desired position shown in the drawingin which it extends parallel to the planes of said anode rings.

The member 25 includes a first portion 26 shaped to fit substantiallytightly in the looped portion of the inductive loop and a second portion27 corresponding in width generally to the distance between the outerand inner walls 13 and 15, respectively, of the cavity. Thus; the member25, when positioned in the cavity inthe manner shown in Figure 1,, holdsthe-loop 23- in the desired position. Assisting in this functionandinsuring contact between the Ioopend=24 and the anode-ringengaged'there by isa planar insulative member 28 having preferably thesame general width as the member-28 iositioned between the loop and thecover 17 of the cavity. The member 28 can also be formed of Teflon andcooperates with the member 25 tohold the loop in the desired positionshown wherein it makes electrical contact with one of the anode ringsand is positioned in close relation to the ceramic wall member disposed"between the anode rings. If desired the loop can abut-the ceramic wallmember between the anode rings; however, it is to be understood one ofsaid anode rings of said magnetron.

3. In combination, an interdigital magnetron including an envelopehaving a pair of anode ringsv sealed in axially spaced relation in thewall of said envelope and separated by an insulative section of saidwall, a reentrant resonator that such abutment is not essential to thedesired operation of my circuit.

While I have shown and described a specific embo'dig ment of myinvention I' do not desire my invention to be limited to the particularform shown and described, and I intend by the appended claims to coverall modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by'ljetters Patent of theUnited States is:

1. In combination, an interdigital magnetron including an evacuatedenvelope having a longitudinally spaced pair of anode rings sealedthrough the wall of said envelope and separated by an insulated sectionof said wall, a

cavity having said magnetron motmted therein and including radiallyspaced inner and outer side walls and axially spaced opposed transverseend walls, said end walls being apertured and including, coaxialcontactsurfaces each making circumferential electrical contact with oneof said anodevrings, a coaxial line including outer and innerconductors, said outer conductor extending radially from the outer sidewall of said cavity, said inner conductor including a flattened J-shapedinductive loop which is substantially wide relative to the portion ofsaid inner conductor in said outer conductor, said inductive loopextending radially inwardly in saidcavity and with the inner end portiondisposed externally of saidenvelope and between radially protrudingportions of said anodein close relation to the wall portion of,jsaid'lenvelope between said rings, and insulative means in' saidcavity-holding said loop in position between saidanode ringsiwiththerturned back end portion of said loop engagingand'fmalting;electricalcontact with one of said anode rings.

'4. The combination according to claim 3, wherein the flattened portionof said loop extends parallel to the planes of said anode rings and saidinsulative means comprises a first member engaging one side of said loopand has a portion fitted between said inner and outer walls of, saidcavity and. another portion fitted inthe looped. portion of saidinductive loop, said insulative means further includes a second memberengaging the opposite sideoff said loop, and said first and secondmembers are tightly fitted'in said cavity for holding said'lo'op inplace and avoiding rotation thereof out of said parallel position.

References Cited in the file of this patent UNITED STATES. PATENTS.

' 2,578,569- McCarthy Dec. 11, :1 2,653,301 Moore etal Sept. 22, 19532,679,615 Bowie May 25; 1954

